Exhaust muffler



Dec. 1, 1964 D. s. 'rHoMAs 3,159,237

EXHAUST MUF F LER Filed oct. 2e, 1959 5 Sheets-Shee l INVENTOR.

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D. G THOMAS EXHAUST MUFFLER Dec. 1, 1964 3 Sheets-Sheet 2 Filed Oct. 28, 1959 INVENTOR. 22d/Z ms' EITC?.

D. G. THOMAS EXHAUST MUFFLER Dec. l, 1964 Filed Oct. 28, 1959 5 Sheets-Sheet 3 @4M/ff United States Patent O o sassari EXHAUS lvllUlFliLEll Bean Q. Thomas, Stoughton, Wis., assigner to Nelson lt/iuiiler Corporation, Stoughton, Wis., a corporation ol Wisconsin c rin-as on. as, rasa, sa. Ns. sessie 2 claims., tcl. rsi- 42) This invention relates generally to exhaust mulllers for internal combustion engines.

As is well known, the cyclicalrnanner in which internal combustion engines operate causes the exhaust gases to emanate in a pulsating stream. rThis pulsating characteristic of the exhaust gas stream gives rise to undesirable sound waves, and numerous schemes have been devised to rnulle or attenuate these waves.

One common approach has involved conducting the exhaust gases through a radially apertured tube, the gases being allowed to expand through the apertures into a closed mui'ller chamber. introduction ot an acoustically absorbent material in the muler 'chamber has proved to increase the degree of attenuation, especially with regard to high frequency sound waves; and acoustical packs consisting of copper, steel or glass wool have been employed.

However, these acoustical absorberits have a number of disadvantages which tend to diminish their etectiveness upon prolonged use. Glass wool is somewhat fragile and is prone to fail, principally by disintegration, when subjected to engine vibration. Copper and steel wools, on the other hand, while more resistant to fatigue failure, are attacked by corrosive constituents in the exhaust gases, rl`he high temperature of the gases is" known to aggravate both of these conditions. Furthermore, all of these Wools tend to collapse or become compacted during use; and this reduction in volume of the acoustical absorbent restricts its propensity for attenuation within the mulller chamber,

Therefore, a general object oi the present invention is to provide va new and improved muler construction.

Another object of the invention is to provide a muffler construction yhaving improved sound attenuation characteristics.

Yet another object ofthe invention is to provide a mutllerconstruction in which the attentuation properties are not degraded during use.

Still another object of the invention is to provide a mutllcr which is both simple and economical to manufacture.

Additional objects and features of the invention petain to the particular' structures and arrangements whereby the above objects are attained.

The invention will be better understood by reference to the following disclosure and drawings forming a part thereof, wherein:

FlGql is a side elevational view partially in crosssection and partially in broken outline showing a straightthrough style mulller constructed in accordance with the invention; Y

llG. 2 is a side elevational View partially in lcrosssection and partially in broken outline showing another straight-through style mutller constructed in accordance with the invention; l

FlG. 3 is a side elevational View partially in crosssection and partially in broken outline showing still another modified straight-through style muiller constructed in accordance with the invention; 4

FlG. 4 is a side elevational View in cross-section of a devious-path stylel muffler constructed inaccordance with the invention; n

FlG. 5 is a side elevational view partially in crosssection and partially in broken outline showing a two- "ice pass style mutller constructed in accordance with the invention;

FlG. 6 is a side elevational view partially in crosssection and partially in broken outline showing a plug style muiiler constructed in accordance with the invention;

FIG. 7 is a side elevational view in cross-section of a return-flow style muffler constructed in accordance with the invention;

.lrllG. 8 is a view through the section 5 3 of FIG. 6;

FlG. 9 is a view through the section 9-9 of FIG. 7;

FlG. l0 is a side elevational view in cross-section of a modilicd straight-through style muiller constructed accordance with the invention;

lilG. 11 is a side elevational view in cross-section of a modified plug style mutller constructed in accordance with the invention;

FIG. 12 is a side elevational view in cross-section of still another modified straight-through style mumer constructed in accordance with the invention;

3lG. i3 is a view through the section lill of FIG. l2; and

lilG. 14 is an enlarged, fragmentary, cross-sectional iew ol one of the sound attenuating materials employed in the invention.

The invention comprehends the use and controlled modification of certain, relatively new materials which have not heretofore been employed in mutller construction and manufacture. rlibe rst of these materials is metal foam of the closed cell type as particularly described and claimed in US. Patent No. 2,751,289, granted lune 19, 1956, to l. C. Elliott. Since this material has a sponge-like appearance and since a major portion of the bubbles or cells are not interconnect-ed, it will be referred to hereinafterk as closed cell vesicular metal. y

A second material, the use of which is comprehended in the present invention, is'metal foam of forarninous nature, i.e. having intercom iunicating cells. To distinguish it from the first described material, this second material will be referred to hereinafter' as open cell vesicular metal.

Whereas closed cell vesicular metal is produced by quenching the foaming, molten mass while each .bubble is completely enveloped by the lluid metal, open cell vesicular metal is produced by quenching the mass while the bubbles are at theV stage of incipient agglomeration and the vast majority of the bubbles intercommunicate. @pen cell vesicular metal is illustratedin FlG. lllwhere a metal matrix A delines a network of interconnected voids or cells B.

in the production of either open or closed cell vesicular metal, when the molten mass is poured into ak cold mold or otherwise quenched, ythe metal at the surface coalesces or ilows together forming a solid, non-cellular skinor casing C. This skin ymay be used toadvantage as will be brought out hereinafter.

Another material embraced 'oy the present invention is metallic honeycomb which is manufactured by welding specially shaped metal sheets together' and subsequently expanding the Welded assembly into a structure having an appearance similar to a honeycomb. Since this material can be fa ricated to have the individual cells interconnected or impertorate, the two forms will be hereinaiter referred to, respectively, as open cell metal honeycomb and closed cell metal honeycomb.v

With detailed reference now to the drawings, specifically to FlG. vl, a straight-through style mutllerindicated generally at 2li includes a housing or chell 22 of cylindrical or other suitable cross-section. Headers or platesrZd are atllxed to shell Z2, to close ofi the e'ndswhile a radially apertured tube 26 is located coaxially within the shell arrasar 3 22 extending through plates 24 so as to provide inlet and outlet means. Advantageously, tube 26 is pressed, welded or otherwise suitably secured to plates 24 and is adapted to be coupled to the exhaust pipe of an internal combustion engine, not shown.

In accordance with a feature of the invention, a number of centrally cored, sound attenuating discs 28 are arranged in axially spaced-apart relationship within the housing 22 and fitted about the tube 26. Discs 28 are of either the open or closed cell type of vesicular metal. However, when the closed cell type of material is employed, apertures 30 in tube 26 are appropriately disposed in communication with the spaces between the discs whereas, when the open cell type of materialis utilized, apertures 32 are arranged to communicate directly with the discs 28 as shown. In either case, it is ladvantageous to expose the cells on the outer surface of the discs, as for example by machining away any surface metal closing olf the individual pores or cells, so that the energy of the entering sound waves may be absorbed by the cell surfaces.

In FIG. 2, a straight-through style muffler t? includes a shell 42 closed olf by centrally apertured headers 44 to which are welded or other wise suitably affixed flanged, hollow end fittings 46.

A number of sound attenuating discs 4ta are fitted within 'the housing 42; and since muier 4t) does not incorporate a central, longitudinally extending tube, it has proved advantageous to punch or drill the discs 4S with axial bores such as are shown at 50. As will be recognized, bores 50 may be arranged longitudinally aligned or eccentric as is desired.

By means of the extent and arrangement of the bores Si), it is possible to maintain a planned relationship between acoustical attenuation and back pressure, specifically by achieving proper balance of cell volume and passageways.

Discs 48 are of either the open or closed cell type of vesicular metal; and as in the embodiment of FIG. 1, it is advantageous, in any event, to expose the cells at the outer surface of the discs. As will become apparent, only sound waves enter the closed cell vesicular metal discs; but both sound waves and exhaust gases enter the open cell vesicular metal discs.

Turning now to FIG. 3, a modified straight-through style mufiier 69 is shown constructed with a housing 62 having 'plates 64 welded or otherwise suitably secured closing oil its ends and having flanged, hollow end fittings 66 providing openings into the interior of housing 62. Before the plates 64 are afhxed, a sound attenuating element 68 corresponding in size and shape to the interior of housing 62 is inserted into the housing. The element 68 is fashioned from open cell vesicular metal and is desirably fashioned to have a central bore '70 communicating the opposite end fittings 6d. Bore '70 may be provided by drilling the member 65 so as to expose a multiplicity of the individual cells of which member 68 is comprised.

Because of the open cell nature of the member 68, it will become apparent that exhaust gases passing through the mutiler 60 expand and follow labyrinthine paths through the member 68 whereby the undesirable sound waves associated with the exhaust gases become attenuated.

The vesicular metal described herein inherently possesses a surface skin of solid metal in its as-cast condition. This skin is employed to advantage as the housing and headers of the devious-path style muier 30 shown in FIG. 4, the combination housing-headers being designated by the numeral 82. Inlet means and outlet means are provided in the muffler 80 by radially apertured pipe stubs 84 being pressed into blind bores in opposite ends of the structure as shown. As will be recognized, these inlet and outlet means may be positioned axially, eccentrically or in side-entry locations, as is desired.

A vesicular metal element 86 is formed of the open cell type of material; and accordingly, exhaust gases are allowed to follow devious paths through the cellular structure of element 86 from the exposed pores of two spacedapart areas 8S located at the ends of the pipe stubs 84.

In FIG. 5, a mufller 10i) of the two-pass style employs the as-cast skin for the shell 1492, and two lengths of radially apertured pipe or tubing 104 are secured in the vesicular metal element 1116 to extend their open ends beyond each other in opposite directions. The cellular element 16 is necessarily of the open cell type in order to provide paths communicating the two pipes 104.

With reference now to FIGS. 6 and 8, a plug style muffler is constructed with a cylindrical shell 122 comprising the cast metal skin referred to hereinabove' encompassing an element 124 of open cell vesicular metal. At opposite ends of the muffler 120, flanged, hollow fittings 126 are welded to the shell 122. The fittings 126 are arranged to be coaxial with the blind bores 128 provided in element 124.

Advantageously, the mold which produces element 124 is cored so as to form the bores 128 with a solid plug 130 closing ot the common end of the bores. Subsequently, the surface of the bores 123 is etched or machined to expose the pores so as to allow exhaust gases to pass from one fitting 126 through the labyrinthine paths in the element 124ito the other fitting 126.

The embodiment shown in FIGS. 7 and 9 comprises a return-flow style mufder 14h in which two pipes or tubes 142 preferably radially apertured with holes 143, are pressed into parallel blind bores provided in a cylindrical, open cell vesicular metal element 144. The closed end portions 146 of these bores expose the pores of the metal so that the interconnected nature of the pores may provide a path for exhaust gases between the two tubes 142. So as to reduce cost and facilitate manufacture, the ascast skin or" metal is employed for the shell or housing 148 of muffler 140.

Referring now to FiG. l0, a modied straight-through style muler16 incorporates a single hollow, flanged fitting 152 affixed to the housing or shell 164 which conveniently takes the form of the as-cast skin referred to previously. Fitting 162 communicates with a bore 166 which i-s drilled or suitably provided in a vesicular metal element 1&8. For purposes of this embodiment, element 168 is of the closed cell type; and accordingly, a number of smaller, radiating bores 179 are arranged to communicate bore 166 exteriorly. In mutiler 160, the network of unconnected cells primarily serves to isolate the sound waves rather than absorbing them as is the case with networks of interconnected cells.

A muliler 130 of modified plug style and having a solid metal base 182 cast integrally with the case or skin 184 is shown in FIG. l1. Here a tapped hole 186 communi- Cates with a blind bore 18S provided in a vesicular metal element 190 having open cells. In this embodiment, the bore 188 is machined or etched to expose the cells while a number of holes 192 are drilled through the casing 184. The holes 192 provide outlet for the exhaust gases directed through the tapped hole 186 into the labyrinthine passageways in the element 19t).

Turning now to FIGS. 12 and 13, a straight-through style muffler 290 is shown to include a housing or `shell 202 having headers 204 suitably affixed closing off its opposite ends. A pair of anged, hollow fittings 2do are secured to the plates 204 in alignment with the central bores provided in the plates. Within the housing 262, a honeycombed metal element 268 is arranged to provide opposite end chambers 210; and the honeycombed metal Furthermore, the embodiments hereinabove described represent only a limited number of the constructions possible within the purview of the invention; and as will become apparent, structural features described with particular reference to one of the illustrated embodiments may be exchanged for similar structure found in one or more of Ithe other embodiments. Accordingly, it should be understood that the invention is not to be limited to the specific constructions which have been shown and described, rather, the invention is intended to` be limited only by the spirit and scope of the appended claims.

The invention is claimed as follows:

1. An exhaust muffler for internal combustion engines comprising a unitary metal body having an exhaust gas inlet, an exhaust gas outlet and a mass of foamed metal including a network of substantially interconnected cells disposed between said inlet and said outlet in lowpathwise obstructing relationship therewith whereby gases passing from said inlet to said outlet are caused to follow labyrinthine paths through the interconnected cells of said mass of foamed metal for attenuating sound waves carried by said gases.

2. An exhaust muffler for internal combustion engines comprising a unitary metal body having an exhaust gas inlet, an exhaust gas outlet and a mass of foamed metal 25 including a network of substantially interconnected cells disposedI between said inlet and said outlet in ilowpathwise obstructing relationship therewith whereby gases passing from said inlet to said outlet are caused to follow labyrinthne paths through the interconnected cells of said mass of foamed metal for attenuating sound waves carried by saidV gases, said metal body further having a substantially inperforate metal skin integrally connected to said network of cells exteriorly thereof whereby to form a housing for said unitary metal body.

References Cited in the iile of this patent UNITED STATES PATENTS 1,968,456 Kliefoth July 31, 1934 2,065,343 Moore et al. Dec. 22, 1936 2,072,961 Nelson Mar. 9, 1937 2,073,951 Servais Mar. 16, 1937 2,392,559 Varina Jan. 8, 1946 2,434,775 Sosnick Jan. 20, 1948 2,523,260 Campbell Sept. 26, 1950 2,553,016 Sosnick May 15, 1951 2,576,610 Kunzog Nov. 27, 1951 2,633,703 Tenney et al. Apr. 7, 1953 2,661,238 Osti Dee. 1, 1953 2,751,289 Elliott June 19, 1956 FOREIGN PATENTS 615,147 France Oct. 2, 1926 961,667 France Nov. 21, 1949 

1. AN EXHAUST MUFFLER FOR INTERNAL COMBUSTION ENGINES COMPRISING A UNITARY METAL BODY HAVING AN EXHAUST GAS INLET, AN EXHAUST GAS OUTLET AND A MASS OF FOAMED METAL INCLUDING A NETWORK OF SUBSTANTIALLY INTERCONNECTED CELLS DISPOSED BETWEEN SAID INLET AND SAID OUTLET IN FLOWPATHWISE OBSTRUCTING RELATIONSHIP THEREWITH WHEREBY GASES PASSING FROM SAID INLET TO SAID OUTLET ARE CAUSED TO FOLLOW LABYRINTHINE PATHS THROUGH THE INTERCONNECTED CELLS OF SAID MASS OF FOAMED METAL FOR ATTENUATING SOUND WAVES CARRIED BY SAID GASES. 